Spring boot（二）递归查询商品分类集合实现

查询商品顶级（父级）分类

• 实体商品分类对象

@Data
public class Category {
    private Integer id;

    private Integer parentId;

    private String name;

    private Boolean status;

    private Integer sortOrder;

    private Date createTime;

    private Date updateTime;
}

• vo类

@Data
public class CategoryVo {

	private Integer id;

	private Integer parentId;

	private String name;

	private Integer sortOrder;

	private List<CategoryVo> subCategories;
}

	@Override
	public ResponseVo<List<CategoryVo>> selectAll() {
		//查询商品分类集合
		List<Category> categories = categoryMapper.selectAll();
		//获取顶级分类集合
		//实现jdk8的 lambda + stream
		List<CategoryVo> categoryVoList=categories.stream()
				.filter(x->x.getParentId().equals(ROOT_PARENT_ID)) //判断是否为父级分类
				.map(x-> category2CategoryVo(x)) //对象copy
	  .sorted(Comparator.comparing(CategoryVo::getSortOrder).reversed()) //排序
				.collect(Collectors.toList()); //收集到集合中

		//查询子目录
		findSubCategory(categoryVoList, categories);

		return ResponseVo.success(categoryVoList);
	}

• 对象copy方法

private CategoryVo category2CategoryVo(Category category) {
	CategoryVo categoryVo = new CategoryVo();
	BeanUtils.copyProperties(category, categoryVo);//spring 自带copy工具方法
	return categoryVo;
}

查询子级分类方法实现

/**
* 查询子级分类
* @param categoryVoList  父级分类集合
* @param categories  所以的商品分类集合
*/
private void findSubCategory(List<CategoryVo> categoryVoList, List<Category> categories) {
		for (CategoryVo categoryVo : categoryVoList) {
			List<CategoryVo> subCategoryVoList = new ArrayList<>();
			for (Category category : categories) {
				//如果查到内容，设置subCategory, 继续往下查
				if (categoryVo.getId().equals(category.getParentId())) {
					CategoryVo subCategoryVo = category2CategoryVo(category);
					subCategoryVoList.add(subCategoryVo);
				}
				subCategoryVoList.sort(Comparator.comparing(CategoryVo::getSortOrder).reversed());//对根据对象字段sortOrder对集合进行排序（不要求排序的忽略）
				categoryVo.setSubCategories(subCategoryVoList);
				//递归查询（查询当前分类是否还有子级）
				findSubCategory(subCategoryVoList, categories);
			}
		}
	}

表结构

表数据